Sikhote-Alin meteorite

Sikhote-Alin meteorite
An iron meteorite fell on the Sikhote-Alin Mountains, in southeastern Russia, in 1947. Large iron meteorite falls have been witnessed and fragments recovered but never before, in recorded history, a fall of this magnitude. An estimated 23 tonnes of fragments survived the fiery passage through the atmosphere and reached the Earth.
Impact
At around 10:30 AM on 12 February 1947, eyewitnesses in the Sikhote-Alin Mountains, Primorye, Soviet Union, observed a large bolide brighter than the sun that came out of the north and descended at an angle of about 41 degrees. The bright flash and the deafening sound of the fall were observed for around the point of impact not far from Luchegorsk and approximately northeast of Vladivostok. A smoke trail, estimated at long, remained in the sky for several hours.
As the meteor, traveling at a speed of about , entered the atmosphere, it began to break apart, and the fragments fell together, some burying themselves deep. At an altitude of about , the largest mass apparently broke up in a violent explosion called an air burst.
On November 20, 1957 the Soviet Union issued a stamp for the 10th anniversary of the Sikhote-Alin meteorite shower. It reproduces a painting by P. I. Medvedev, a Soviet artist who witnessed the fall: he was sitting in his window starting a sketch when the fireball appeared, so he immediately began drawing what he saw.
Orbit
Because the meteor fell during daytime, it was observed by many eyewitnesses. Evaluation of this observational data allowed V. G. Fesenkov, then chairman of the meteorite committee of the USSR Academy of Science, to estimate the meteoroid's orbit before it encountered the Earth. This orbit was ellipse-shaped, with its point of greatest distance from the sun situated within the asteroid belt, similar to many other small bodies crossing the orbit of the Earth. Such an orbit was probably created by collisions within the asteroid belt.
Size
Sikhote-Alin is a massive fall with the pre-atmospheric mass of the meteoroid estimated at approximately . A more recent estimate by Tsvetkov (and others) puts the mass at around .
Krinov estimated the post-atmospheric mass of the meteoroid at some .
Strewn field and craters
The strewn field for this meteorite covered an elliptical area of about . Some of the fragments made impact craters, the largest of which was about across and deep. Fragments of the meteorite were also driven into the surrounding trees, embedding themselves.
Composition and classification
The Sikhote-Alin meteorite is classified as an iron meteorite belonging to the meteorite group IIAB and with a coarse octahedrite structure. It is composed of approximately 93% iron, 5.9% nickel, 0.42% cobalt, 0.46% phosphorus, and 0.28% sulfur, with trace amounts of germanium and iridium. Minerals present include taenite, plessite, troilite, chromite, kamacite, and schreibersite.
Specimens
Specimens of the Sikhote-Alin Meteorite are basically of two types:
individual, thumbprinted or regmaglypted specimens, showing fusion crust and signs of atmospheric ablation
shrapnel or fragmented specimens, sharp-edged pieces of torn metal showing evidence of violent fragmentation
The first type probably broke off the main object early in the descent. These pieces are characterized by regmaglypts (cavities resembling thumb prints) in the surface of each specimen. The second type are fragments which were either torn apart during the atmospheric explosions or blasted apart upon impact on the frozen ground. Most were probably the result of the explosion at altitude.
A large specimen is on display in Moscow. Many other specimens are held by Russian Academy of Science and many smaller specimens exist in the collectors' market.
See also
Glossary of meteoritics
Meteorite
Meteorite fall
Chelyabinsk Meteor
List of meteor air bursts
References
External links
Meteorites found in Russia
Primorsky Krai
Modern Earth impact events
Holocene impact craters
Geography of Russia
1947 in science
1947 in the Soviet Union
meteorite
February 1947 events in Asia
1947 natural disasters